1. Field of the Invention
This invention relates to the field of data communications, and in particular to an extender for data cables.
2. Description of Related Art
Traditionally, computer peripherals, such as printers, scanners and the like, have been connected to the computer by serial or parallel cables. More recently, in 1995, the Universal Serial Bus has been developed as a substitute for the traditional method. The USB defines an expansion bus, which makes adding peripherals to a computer system as easy as hooking up a telephone to a wall jack. This was achieved through the use of PC host controller hardware and software, robust connectors and cable assemblies, peripheral friendly master-slave protocols, and expandable multi-port hubs.
As part of on-going improvement efforts in this area, a higher bandwidth version of the USB bus, known as USB 2.0 is being developed by a team from Compaq, Hewlett Packard, Intel and others. USB 2.0 is backward compatible with existing USB systems and offers speeds potentially as high as 480 Mbs.
The problem with existing cabling, however, is that it is limited to distances of about five meters when the bandwidth reaches hundreds of megabits per second.
An object of the invention is to extend the range of existing USB cabling.
According to the present invention an extender for an electrical data bus including a power line, comprising first and second electrical connectors for connection to respective electrical connectors attached to respective electrical data buses, each of said fist and second electrical connectors comprising a data interface circuit for communication with a respective said electrical bus, an optical transmitter and optical receiver electrically connected to said data interface circuit, driver circuits for said optical transmitter and optical receivers, said driver circuits obtaining power from the power line on the local electrical data bus, and a optic fiber connected between said optical transmitters and receivers at respective first and second electrical connectors to transfer data optically between said first and second electrical connectors.
The data bus is preferably a universal serial bus (USB), preferably a high bandwidth USB 2.0 bus with speeds up to 480 Mbs or higher.
The fiber optic cable is preferably plastic optic fiber cable. The transmitters and receivers are preferably of the type described in our co-pending application serial number GB 0011065.0, the contents or which are herein incorporated by reference.
The components at each end of the optical fiber are preferably all integrated into a unitary plastic connector housing, which interfaces directly with the electrical connector on the bus. This is preferably of the type that makes a snap fit with the electrical connector attached to the bus.
Although relying on optical components, the extender is self-powered since the power for the driver circuits is derived from the power line on the bus.
The invention also provides a method of extending the range of an electrical data, bus including a power line and signal lines, comprising connecting first and second electrical connectors to respective electrical connectors attached to respective electrical data buses, each of said first and second electrical connectors comprising a data interface circuit communicating with a respective said electrical bus, an optical transmitter and optical receiver electrically connected to said data interface circuit, driver circuits for said optical transmitter and optical receivers; deriving power for said driver circuits power from the power line on the local electrical data bus; and transferring data between said optical transmitter and receivers at said respective first and second connectors over an optic fiber.
The invention further provides an electrical data bus including a power line, comprising a first electrical connector for connection to an electrical connector attached to an electrical data bus and a second optical connector for connection to an optic fiber, said first electrical connector comprising a data interface circuit for communication with a respective said electrical bus, an optical transmitter and optical receiver electrically connected to said data interface circuit, driver circuits for said optical transmitter and optical receivers, said driver circuits obtaining power from the power line on the local electrical data bus, and a optic fiber connected between said optical transmitters and receivers and said second optical connector.